A convex double-layer composite small-caliber artificial blood vessel and its preparation method

Abstract

The present invention belongs to the field of medical devices, and specifically relates to a convex double-layer composite small-caliber artificial blood vessel and a preparation method thereof. The convex double-layer composite small-caliber artificial blood vessel includes an inner lining layer, an artificial blood vessel inner layer and an artificial blood vessel outer layer; the inner lining layer is made of a soluble material, and the middle part of the inner lining layer bulges radially outward; the artificial blood vessel inner layer and the artificial blood vessel outer layer are sequentially arranged outside the inner lining layer, and present a shape in which the middle part bulges radially outward under the support of the inner lining layer; the artificial blood vessel outer layer is a porous loose structure. The small-caliber artificial blood vessel of the present invention has a two-layer structure and is convex in shape. The combination of the dip coating layer and the electrospinning layer is beneficial to ensuring the suture retention strength and bursting pressure of the blood vessel, and can also enable the blood vessel to maintain a certain elasticity and porosity; the convex shape can make up for the lack of compliance of the artificial blood vessel, and is beneficial to reducing blood flow disturbance at the anastomosis, thereby reducing the risk of intimal hyperplasia.

Description

Technical Field

[0001] The present invention belongs to the field of medical devices, and in particular relates to a convex double-layer composite small-caliber artificial blood vessel and a preparation method thereof. Background Art

[0002] Artificial blood vessel replacement is a common surgical procedure for treating arterial disease in vascular surgery. Large and medium-caliber artificial blood vessels have been clinically used with satisfactory results. However, small-caliber artificial blood vessels (with an inner diameter less than 6 mm) are prone to postoperative thrombosis and intimal hyperplasia, leading to restenosis and low patency rates, which remain unresolved.

[0003] The pathogenesis of intimal hyperplasia (INTH) is highly complex, but hemodynamic abnormalities caused by a mismatch in compliance between prosthetic and host vessels are the primary mechanical triggers of intimal hyperplasia. Compliance refers to the ease with which a vessel deforms under pulsatile pressure. High compliance indicates greater deformation under relatively small external forces. For hollow organs, high compliance translates to greater distensibility, meaning that a relatively small transmural pressure can induce a significant change in intraluminal volume. While various approaches have been employed to improve the compliance of prosthetic vessels, the compliance of most prosthetic vessels remains lower than that of the host vessel due to current limitations in available materials and fabrication methods. Consequently, when the diameter of a prosthetic vessel matches that of the host vessel, its radial expansion displacement is often smaller than that of the host vessel, leading to abnormal changes or disturbances in blood flow at the anastomosis, which in turn can induce intimal hyperplasia.

[0004] In the prior art, most artificial blood vessels are straight with a circular cross-section. However, the invention patent, "A Multi-layer Composite Artificial Blood Vessel with Adjustable Compliance," with publication number 109498209A and publication date March 22, 2019, discloses an artificial blood vessel composed of three nested layers of composite foam tubes. The composite foam tubes are made from a blend of PCL, PLA, and TPU, with gel or protein filling the spaces between adjacent composite foam tubes. By controlling the composition of PLA, PCL, and TPU, and adjusting the internal pore size and pore size distribution of each layer of composite foam tube, the artificial blood vessel achieves the goal of achieving a ratio of elastic modulus of the outer composite foam tube greater than that of the middle composite foam tube, which is greater than that of the inner composite foam tube, thereby improving the compliance of the artificial blood vessel. The patent's preparation process is relatively complex, and the elastic modulus regulation is relatively complicated.

[0005] The invention patent with publication number "112274699 A" and publication date of January 29, 2021, and the name "Small-caliber tissue-modified composite artificial blood vessel" discloses a small-caliber artificial blood vessel including an outer layer of tissue, an inner layer of tissue and a collagenous tissue. The outer layer of tissue is composed of a blended layer, micron particle pores and an aortic elastic layer, the inner layer of tissue is composed of acellular endocardium, an intimal hyperplasia layer and an anti-thrombotic drug layer, and the collagenous tissue is composed of N-hydroxysuccinimide and carbodiimide. The natural acellular matrix material gives the artificial blood vessel good compliance and cell compatibility. The outer layer is a blended layer of silk fibroin, carboxylated bacterial cellulose and gelatin, which increases the mechanical properties of the blood vessel; the inner side of the inner layer can be modified with different drugs to improve the anti-thrombotic property of the artificial blood vessel and promote the formation of the vascular endothelium. The process involved in this patent is relatively complicated, and mainly relies on raw materials to improve the compliance of the artificial blood vessel, and the effect is limited.

[0006] Therefore, a new approach is needed to reduce the adverse hemodynamic effects of compliance mismatch and thereby reduce the risk of intimal hyperplasia. Summary of the Invention

[0007] The present invention aims to solve the above-mentioned problems and provides a convex double-layer composite small-caliber artificial blood vessel and a preparation method thereof. The risk of intimal hyperplasia is reduced by enlarging the diameter of the middle part of the artificial blood vessel, that is, the diameters of the two ends of the artificial blood vessel are the same as those of the host blood vessel, and the diameter of the middle part is larger than that of the host blood vessel.

[0008] According to the technical solution of the present invention, the convex double-layer composite small-caliber artificial blood vessel includes an inner lining layer, an artificial blood vessel inner layer and an artificial blood vessel outer layer; the inner lining layer is made of a soluble material, and the middle part of the inner lining layer bulges radially outward; the artificial blood vessel inner layer and the artificial blood vessel outer layer are sequentially arranged outside the inner lining layer, and present a shape of bulging radially outward in the middle part under the support of the inner lining layer; the artificial blood vessel outer layer is a porous and loose structure.

[0009] Specifically, the soluble material is a water-soluble polymer, which can eventually dissolve; the porous loose structure of the outer layer of the artificial blood vessel can be formed by electrospinning, which is beneficial to improving the elasticity of the blood vessels and cell proliferation.

[0010] Another aspect of the present invention provides a method for preparing the above-mentioned convex double-layer composite small-caliber artificial blood vessel, comprising the following steps:

[0011] S1: Immerse the cylindrical mold in the release liquid, retain it for 5-10 seconds, then remove it from the release liquid and dry it. Repeat the above operation for multiple layers of dip coating to obtain a mold with a dip coating;

[0012] The diameter of the cylindrical mold is 3-6 mm, and the demoulding liquid is a water-soluble polymer solution;

[0013] S2: removing the dip coating at both ends of the mold with the dip coating to form a convex structure;

[0014] S3: Immerse the convex structure in a demoulding liquid, retain it for 5-10 seconds, then withdraw from the demoulding liquid and dry it; invert the convex structure and repeat the dipping and demoulding liquid operation to obtain a mold with an inner lining layer (demolding layer);

[0015] S4: Dipping the mold with the lining layer into the dipping solution, retaining it for 1-5 seconds, then withdrawing from the dipping solution and drying it; repeatedly inverting the mold with the lining layer and repeating the dipping operation to obtain a mold with an artificial blood vessel inner layer;

[0016] The dipping liquid is a poly (L-lactide)-caprolactone solution or a polyurethane solution;

[0017] S5: using a poly (L-lactide-caprolactone) solution or a polyurethane solution as a spinning solution, performing electrospinning on the surface of the mold with the artificial blood vessel inner layer, and drying to obtain a semi-finished mold;

[0018] S6: removing the inner lining layer in the semi-finished mold, taking out the cylindrical mold, and obtaining the convex double-layer composite small-caliber artificial blood vessel.

[0019] Specifically, the material of the cylindrical mold can be stainless steel.

[0020] Furthermore, in steps S1 and S3, the speed of withdrawing the demoulding liquid is 500-2000 μm / s.

[0021] Furthermore, the demolding liquid is a polyvinyl alcohol solution and / or a polyethylene oxide solution, the concentration of which is 12-18 wt %, and the solvent is a mixture of water and ethanol.

[0022] Furthermore, in step S2, both ends of the mold with the dip coating are immersed in water respectively to remove the dip coating.

[0023] Furthermore, in step S4, the speed of withdrawing the dipping solution is 800-1200 μm / s.

[0024] Furthermore, the concentration of the dipping solution is 5.5-6.5 wt %.

[0025] Furthermore, the dipping solution also includes a pore-forming agent, which may be PEG (polyethylene glycol) or other non-toxic pore-forming agents.

[0026] Furthermore, the concentration of the spinning solution is 7.5-8.5 wt %, and the solute is consistent with that of the dipping solution.

[0027] Furthermore, in step S5, the electrospinning parameters are: the injection pump propulsion speed is controlled at 0.5-1.5 mL / h, the high-voltage DC power supply voltage is controlled at 10-12 kV; the distance between the spinneret and the receiving device is 15-20 cm, the collection device speed is 300-500 rpm, the spinning temperature is 28-32°C, and the spinning relative humidity is <65%.

[0028] Specifically, the above preparation method can be as follows:

[0029] (1) Lining layer (release layer)

[0030] Choose a cylindrical mold made of stainless steel with a diameter of 3-6mm;

[0031] Prepare a water-soluble polymer solution of a certain concentration and dip-coat it on the metal rod, such as polyvinyl alcohol (PVA), polyethylene oxide (PEO), etc.

[0032] Fix the cylindrical mold to the bayonet of the dip coating machine and immerse it in the release liquid at a constant speed, retaining it for 5-10 seconds. Withdraw the mold at a speed of 500-2000μm / s. After withdrawal, hang it to dry at room temperature (25±5℃) for 5-10 minutes. Repeat the above steps for multiple layers of dip coating according to the required diameter of the blood vessel. The more layers, the larger the diameter of the middle section of the blood vessel.

[0033] Fix the mold with the dip coating on the bayonet of the pull-up dip coating machine, immerse one end of the dip coating in deionized water at room temperature for 30 minutes to dissolve the dip coating on one end; invert the mold and use the same method to dissolve the other end of the dip coating, leaving the middle part of the dip coating, thereby forming a convex structure;

[0034] The obtained convex mold is fixed on the bayonet of the dip coating machine and immersed in the release liquid again at a certain speed, and retained for 5-10 seconds; the withdrawal speed is controlled at 500-2000 μm / s, and after hanging and drying at room temperature for 5-10 minutes, the mold is inverted and the above process is repeated for the second layer of dip coating, and then hung and dried at room temperature for 25-40 minutes; thus, the convex blood vessel lining layer or release layer is obtained;

[0035] (2) Artificial blood vessel lining

[0036] The mold with the convex release layer prepared in step (1) is used as the mold;

[0037] Prepare a solution of a certain concentration suitable for preparing artificial blood vessels by dip coating, such as poly (L-lactide-caprolactone) (PLCL), polyurethane, etc.;

[0038] Fix the convex mold on the bayonet of the lifting and dipping coating machine and immerse it in the dipping solution at a certain speed for 1-5 seconds; then withdraw the mold from the solution at a certain speed, and control the withdrawal speed to be 800-1200μm / s; after the dipping is completed, dry the mold in a fume hood for 5-10 minutes, then fix it upside down on the bayonet of the lifting and dipping coating machine, and repeat the above steps for the second layer of dipping. Repeat the above steps for multi-layer dipping according to the thickness requirements of the inner layer of the blood vessel. Since the structure of the dipping coating is dense, the thicker the inner layer, the higher its burst pressure and suture retention strength, but the poorer the elasticity of the artificial blood vessel; the preferred number of layers is 2-8 layers, and the thickness is 50-200μm;

[0039] (3) Outer layer of artificial blood vessel

[0040] Prepare a certain concentration of electrospinning solution, the material is consistent with the material used for the dipping solution

[0041] Immediately fix the convex mold after the inner layer is dipped on the collection device of the electrospinning machine. Electrospinning parameters: The injection pump propulsion speed is controlled at 0.5-1.5mL / h, the high-voltage DC power supply voltage is controlled at 10-12kV; the distance between the spinneret and the receiving device is 15-20cm, the collection device speed is 300-500rpm, the spinning temperature is 28-32℃, and the spinning relative humidity is <65%. The spinning time is controlled according to the required blood vessel thickness. The longer the time, the thicker the electrospinning layer. The appropriate spinning time is controlled according to the total wall thickness of the blood vessel and the ratio of the inner and outer layers of the artificial blood vessel.

[0042] Demolding: After completing the above steps, remove the mold and place it in a fume hood to dry for 12-24 hours. Then, soak it in deionized water to remove the lining. Remove the mold, grasp one end of the metal rod, and use forceps to grasp the blood vessel at the other end. Gently drag and twist to remove the artificial blood vessel. After removal, place it upright in a beaker and dry at room temperature for 10-15 hours. Store in a sealed bag.

[0043] The technical solution of the present invention has the following advantages over the existing technology: the small-caliber artificial blood vessel of the present invention has a two-layer structure and is convex in shape. The combination of the dip coating layer and the electrospinning layer is beneficial to ensuring the suture retention strength and bursting pressure of the blood vessel, and can also enable the blood vessel to maintain a certain elasticity and porosity; the convex shape, on the one hand, does not affect the anastomosis between the two ends of the artificial blood vessel and the host blood vessel; on the other hand, under pulsating pressure, the radial expansion displacement of the convex part of the artificial blood vessel can be consistent with the host blood vessel, thereby compensating for the lack of compliance of the artificial blood vessel, and is beneficial to reducing blood flow disturbance at the anastomosis, thereby reducing the risk of intimal hyperplasia. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 This is a physical diagram of the artificial blood vessel obtained in Example 1.

[0045] Figure 2 This is a physical diagram of the artificial blood vessel obtained in Example 2. DETAILED DESCRIPTION

[0046] The present invention will be further described below with reference to the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it. However, the embodiments are not intended to limit the present invention.

[0047] Example 1:

[0048] (1) Dip coating

[0049] 1. Convex inner lining

[0050] 1.1 Mold selection: cylindrical mold, made of stainless steel, mold diameter 5mm.

[0051] 1.2 Coating liquid preparation:

[0052] 7.5 g of PVA was weighed and a 15% PVA solution was prepared as a water-soluble polymer solution. The solvent was deionized water and anhydrous ethanol in a 50:50 ratio.

[0053] 1.3 Dip coating process:

[0054] 1.3.1 Fix the cylindrical mold on the bayonet of the dip coating machine and immerse it in the PVA solution at a speed of 5000 μm / s for 10 seconds;

[0055] 1.3.2 Remove the mold from the PVA solution at a speed of 1200 μm / s. After hanging to dry at room temperature for 5 minutes, immerse it in the PVA solution at a speed of 5000 μm / s. To prevent the PVA layer from redissolving, shorten the single retention time to 1 second.

[0056] 1.3.3 Repeat step 1.3.2 for 4 coats of dip coating. Hang the mold to dry at room temperature for 30 min.

[0057] 1.3.4 After drying, fix the cylindrical mold upside down on the bracket of the pull-up dip coating machine, repeat step 1.3.2 and dip-coat 4 layers of PVA again;

[0058] 1.3.5 Repeat the above steps for multiple layers of PVA coating, depending on the required diameter of the vessel. The more layers, the larger the diameter of the middle section of the vessel. Apply a total of 16 layers of PVA. After PVA coating, hang to dry at room temperature for 12 hours.

[0059] 1.3.6 Secure the mold coated with 16 layers of PVA coating to the bracket of the pull-up dip coating machine. Depending on the required length of the enlarged section of the blood vessel, immerse one end of the mold in deionized water at room temperature for 30 minutes to dissolve the excess PVA coating. Remove the mold from the deionized water, invert it, and secure it to the bracket of the pull-up dip coating machine. Repeat the above steps to dissolve the excess PVA coating on the other end of the mold.

[0060] 1.3.7 After the excess PVA layer is dissolved, fix the resulting convex mold on the bayonet of the dip coating machine and immerse it in the PVA solution at a speed of 5000 μm / s for 10 seconds;

[0061] 1.3.8 Remove the mold from the PVA solution at a speed of 1200 μm / s. After hanging to dry at room temperature for 5 minutes, immerse it in the PVA solution at a speed of 5000 μm / s. To prevent the PVA layer from redissolving, shorten the single retention time to 1 second.

[0062] 1.3.9 Repeat step 1.3.8 for the third layer of dip coating based on the transition between the raised section and both ends of the mold. The more dip coatings you do, the better the transition. After dipping, hang the mold to dry at room temperature for 30 minutes.

[0063] 1.3.10 After drying, fix the convex mold upside down on the bracket of the pull-up dip coating machine, repeat step 1.3.8 and dip-coat 3 layers of PVA again;

[0064] 1.3.11 After the PVA layer is dip-coated, it is fixed on the bracket of the dip-pull coating machine and dried in a ventilated place at room temperature for 12 hours to obtain a convex blood vessel mold with 6 layers of PVA coated on both ends and 22 layers of PVA coated in the middle.

[0065] 2. Artificial blood vessel lining

[0066] 2.1 Mold selection: The convex mold obtained in the previous step is coated with 6 layers of PVA at both ends and 22 layers of PVA in the middle.

[0067] 2.2 Preparation of dipping solution:

[0068] Weigh 2g of PLCL and prepare a 6% PLCL solution as the dipping solution. The solvent is hexafluoroisopropanol, and 1g of PEG is added as a porogen.

[0069] 2.3 Dip coating process:

[0070] 2.3.1 Fix the PVA-coated convex mold on the bayonet of the pull-up dip coating machine and immerse it in the PLCL solution at a speed of 5000μm / s for 5s; then withdraw the mold from the PLCL solution at a speed of 1000μm / s;

[0071] 2.3.2 After dip coating, dry the mold in a fume hood for 5 minutes, then invert and secure it to the clamping position of the pull-up dip coating machine. Repeat the above steps for the second dip coating. Repeat the above steps for a total of 4 dip coating layers, depending on the thickness of the blood vessel. The dip coating thickness is now approximately 100 μm.

[0072] (2) Electrospinning layer

[0073] 1. Spinning solution preparation:

[0074] The PLCL solution with a concentration of 8% was prepared in accordance with the polymer of the dipping solution, and the solvent was hexafluoroisopropanol.

[0075] 2. Electrospinning process:

[0076] 2.1 Immediately secure the dip-coated convex mold to the collection device of the electrospinning machine. Electrospinning parameters: syringe pump speed controlled at 1 mL / h, high-voltage DC power supply voltage controlled at 12 kV; distance between spinneret and receiver 18 cm, collection device speed 500 rpm, spinning temperature 28-32°C, relative humidity <65%.

[0077] 2.2 According to the required blood vessel thickness, the electrospun layer was spun for 2.5 h and the thickness was about 200 μm.

[0078] 2.3 Demolding: After completing the above steps, remove the mold, place it in a fume hood to dry for 12 hours, and then soak it in deionized water to remove the PVA coating. An appropriate amount of anhydrous ethanol can be added to promote the dissolution of PVA. After soaking for 12 hours, take out the mold, hold one end of the metal rod, clamp the blood vessel at the other end with tweezers, gently drag and rotate it to remove the artificial blood vessel. After removal, place it upright in a beaker and dry it at room temperature for 12 hours. Then take the artificial blood vessel out of the beaker and store it in a ziplock bag. The resulting convex blood vessel is as follows: Figure 1 shown.

[0079] Example 2

[0080] (1) Dip coating

[0081] 1. Convex inner lining

[0082] 1.1 Mold selection: cylindrical mold, made of stainless steel, mold diameter 5mm.

[0083] 1.2 Preparation of dipping solution:

[0084] 7.5 g of PVA was weighed and a 15% PVA solution was prepared as a water-soluble polymer solution. The solvent was deionized water and anhydrous ethanol in a 50:50 ratio.

[0085] 1.3 Dip coating process:

[0086] 1.3.1 Fix the cylindrical mold on the bayonet of the dip coating machine and immerse it in the PVA solution at a speed of 5000 μm / s for 10 seconds;

[0087] 1.3.2 Remove the mold from the PVA solution at a speed of 1200 μm / s. After hanging to dry at room temperature for 5 minutes, immerse it in the PVA solution at a speed of 5000 μm / s. To prevent the PVA layer from redissolving, shorten the single retention time to 1 second.

[0088] 1.3.3 Repeat step 1.3.2 for 7 coats of dip coating. Hang the mold to dry at room temperature for 30 min.

[0089] 1.3.4 After drying, fix the cylindrical mold upside down on the bracket of the pull-up dip coating machine, repeat step 1.3.2, and dip-coat 7 layers of PVA again;

[0090] 1.3.5 Apply 14 layers of PVA to the vessel according to its diameter. After PVA coating, hang the vessel to dry at room temperature for 12 hours.

[0091] 1.3.6 Secure the mold coated with 14 layers of PVA coating to the bracket of the dip coating machine. Depending on the required length of the enlarged section of the blood vessel, immerse one end of the mold in deionized water at room temperature for 30 minutes to dissolve the excess PVA coating. Remove the mold from the deionized water, invert it, and secure it to the bracket of the dip coating machine. Repeat the above steps to dissolve the excess PVA coating on the other end of the mold.

[0092] 1.3.7 After the excess PVA layer is dissolved, fix the resulting convex mold on the bayonet of the dip coating machine and immerse it in the PVA solution at a speed of 5000 μm / s for 10 seconds;

[0093] 1.3.8 Remove the mold from the PVA solution at a speed of 1200 μm / s. After hanging to dry at room temperature for 5 minutes, immerse it in the PVA solution at a speed of 5000 μm / s. To prevent the PVA layer from redissolving, shorten the single retention time to 1 second.

[0094] 1.3.9 After dipping, hang the mold to dry at room temperature for 30 minutes;

[0095] 1.3.10 After drying, fix the convex mold upside down on the bracket of the pull-up dip coating machine, repeat step 1.3.8 and dip-coat 2 more layers of PVA;

[0096] 1.3.11 After the PVA layer is dip-coated, it is fixed on the bracket of the dip-pull coating machine and dried in a ventilated place at room temperature for 12 hours to obtain a convex blood vessel mold with 4 layers of PVA coated on both ends and 18 layers of PVA coated in the middle.

[0097] 2. Artificial blood vessel lining

[0098] 2.1 Mold selection: The convex mold obtained in the previous step is coated with 4 layers of PVA at both ends and 18 layers of PVA in the middle.

[0099] 2.2 Preparation of dipping solution:

[0100] Weigh 2g of PLCL and prepare a 6% PLCL solution as the dipping solution. The solvent is hexafluoroisopropanol, and 1g of PEG is added as a porogen.

[0101] 2.3 Dip coating process:

[0102] 2.3.1 Fix the PVA-coated convex mold on the bayonet of the pull-up dip coating machine and immerse it in the PLCL solution at a speed of 5000μm / s for 5s; then withdraw the mold from the PLCL solution at a speed of 900μm / s;

[0103] 2.3.2 After dip coating, dry the mold in a fume hood for 5 minutes, then invert and secure it to the clamping position of the pull-up dip coating machine and repeat the above steps for the second layer of dip coating. Repeat the above steps for two layers of dip coating according to the thickness requirements of the blood vessels. The dip coating thickness is about 50μm.

[0104] (2) Electrospinning layer

[0105] 1. Spinning solution preparation:

[0106] The PLCL solution with a concentration of 8% was prepared in accordance with the polymer of the dipping solution, and the solvent was hexafluoroisopropanol.

[0107] 2. Electrospinning process:

[0108] 2.1 Immediately secure the dip-coated convex mold to the collection device of the electrospinning machine. Electrospinning parameters: syringe pump speed controlled at 1 mL / h, high-voltage DC power supply voltage controlled at 12 kV; distance between spinneret and receiver 19 cm, collection device speed 500 rpm, spinning temperature <32°C, relative humidity <65%.

[0109] 2.2 According to the required blood vessel thickness, the electrospun layer was spun for 2 h and the thickness was about 150 μm.

[0110] 2.3 Demolding: After completing the above steps, remove the mold, place it in a fume hood to dry for 12 hours, and then soak it in deionized water to remove the PVA coating. An appropriate amount of anhydrous ethanol can be added to promote the dissolution of PVA. After soaking for 12 hours, take out the mold, hold one end of the metal rod, clamp the blood vessel at the other end with tweezers, gently drag and rotate it to remove the artificial blood vessel. After removal, place it upright in a beaker and dry it at room temperature for 12 hours. Then take the artificial blood vessel out of the beaker and store it in a ziplock bag. The resulting convex blood vessel is as follows: Figure 2 shown.

[0111] Example 3

[0112] Based on Example 1, the dipping solution and spinning solution were replaced with polyurethane solutions, and the solvent was hexafluoroisopropanol (HFIP), with concentrations of 6 wt% and 8 wt%, respectively. The steps for preparing the convex inner lining remained unchanged, resulting in a convex blood vessel mold with six layers of PVA coated on both ends and 22 layers of PVA coated in the middle.

[0113] 1. Artificial blood vessel lining

[0114] 1.1 Mould selection: convex mould with 6 layers of PVA on both ends and 22 layers of PVA in the middle

[0115] 1.2 Dipping liquid: 6wt% polyurethane solution, solvent is hexafluoroisopropanol

[0116] 2.3 Dip coating process:

[0117] 2.3.1 Fix the PVA-coated convex mold on the bayonet of the pull-up dip coating machine and immerse it in the polyurethane solution at a speed of 5000 μm / s for 5 seconds; then withdraw the mold from the polyurethane solution at a speed of 800 μm / s;

[0118] 2.3.2 After dipping, dry the mold in a fume hood for 5 minutes, then fix it upside down on the bracket of the pull-up dip coating machine, and repeat the above steps to perform the second layer of dipping. At this time, the thickness of the dip coating is about 20μm.

[0119] (2) Electrospinning layer

[0120] 1. Spinning solution: The same as the dipping solution polymer, prepare a polyurethane solution with a concentration of 8wt%, and the solvent is hexafluoroisopropanol.

[0121] 2. Electrospinning process:

[0122] 2.1 Immediately secure the dip-coated convex mold to the collection device of the electrospinning machine. Electrospinning parameters: syringe pump speed controlled at 0.8 mL / h, high-voltage DC power supply voltage controlled at 12 kV; distance between spinneret and receiver 18 cm, collection device speed 500 rpm, spinning temperature 28-32°C, relative humidity <65%.

[0123] 2.2 According to the required blood vessel thickness, the electrospun layer was spun for 2.5 h and the thickness was about 180 μm.

[0124] 2.3 Demolding: After completing the above steps, remove the mold and place it in a fume hood to dry for 12 hours. Then, soak it in deionized water to remove the PVA coating. An appropriate amount of anhydrous ethanol can be added to promote the dissolution of the PVA. After soaking for 12 hours, remove the mold. Grasp one end of the metal rod and the blood vessel at the other end with forceps. Gently drag and rotate to remove the artificial blood vessel. After removal, place it upright in a beaker and dry at room temperature for 12 hours. Then remove the artificial blood vessel from the beaker and store it in a ziplock bag.

[0125] Result Analysis

[0126] The mechanical performance evaluation standard of artificial blood vessels according to ISO 7198:1998 was used to test the convex double-layer composite small-caliber artificial blood vessels prepared in Example 1.

[0127] 1. Compliance test

[0128] Keeping the thickness of the artificial blood vessel dip coating and the electrospinning layer unchanged, a straight small-caliber artificial blood vessel with an inner diameter of 5 mm was prepared as a control sample. The compliance of this blood vessel and the convex double-layer composite small-caliber artificial blood vessel prepared in Example 1 was tested. The compliance of the convex double-layer composite small-caliber artificial blood vessel prepared in Example 1 was 2.29% / 100 mmHg, and the compliance of the straight small-caliber artificial blood vessel with the same inner diameter and thickness was 1.57% / 100 mmHg, which proved that the convex blood vessel provided by the present invention has significantly improved and enhanced the compliance of the artificial blood vessel.

[0129] 2. Time-averaged wall shear stress (TAWSS)

[0130] Low wall shear stress (WSS) distribution is one of the biomechanical factors that trigger intimal hyperplasia. It is prone to occur on the host vessel side of the distal anastomosis between the artificial blood vessel and the host vessel. The TAWSS within a single cardiac cycle is often used to measure the magnitude of WSS. Through numerical simulation, the lowest TAWSS at the distal anastomosis of the convex double-layer composite small-caliber artificial blood vessel prepared in Example 1 was 0.029 Pa. The lowest TAWSS at the distal anastomosis of a straight small-caliber artificial blood vessel with the same inner diameter and thickness was 0.016 Pa. This demonstrates that the convex blood vessels provided by the present invention can improve the lowest TAWSS at the distal anastomosis.

[0131] 3. Suture retention strength test

[0132] Suture retention strength tests were performed on the samples according to the test method provided in the ISO7198 standard. The suture retention strength of the convex double-layer composite small-caliber artificial blood vessel prepared in Example 1 was 291.9 cN. The suture retention strength of the human saphenous vein was 179.5-267.2 cN, and the suture retention strength of the internal mammary artery was 137.7-142.8 cN. The suture retention strength of the convex blood vessel provided by the present invention was higher than that of the human saphenous vein and internal mammary artery, ensuring the stability of the artificial blood vessel during transplantation.

[0133] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A convex double-layer composite small-caliber artificial blood vessel, characterized in that: The artificial blood vessel comprises an inner lining layer, an inner artificial blood vessel layer and an outer artificial blood vessel layer; the inner lining layer is made of a dissolvable material, and the middle portion of the inner lining layer bulges radially outward; the inner artificial blood vessel layer and the outer artificial blood vessel layer are sequentially arranged outside the inner lining layer, and are supported by the inner lining layer, and are in a shape in which the middle portion bulges radially outward; the outer artificial blood vessel layer is a porous and loose structure; The method for preparing the convex double-layer composite small-caliber artificial blood vessel comprises the following steps: S1: Immerse the cylindrical mold in the release liquid, retain it for 5-10 seconds, then remove it from the release liquid and dry it. Repeat the above operation for multiple layers of dip coating to obtain a mold with a dip coating; The diameter of the cylindrical mold is 3-6 mm, and the demoulding liquid is a water-soluble polymer solution; S2: removing the dip coating at both ends of the mold with the dip coating to form a convex structure; S3: immersing the convex structure in a demoulding liquid, retaining it for 5-10 seconds, then withdrawing from the demoulding liquid and drying it; inverting the convex structure, repeating the dipping and coating operation to obtain a mold with an inner lining layer; S4: Dipping the mold with the lining layer into the dipping solution, retaining it for 1-5 seconds, then withdrawing from the dipping solution and drying it; repeatedly inverting the mold with the lining layer and repeating the dipping operation to obtain a mold with an artificial blood vessel inner layer; The dipping liquid is a poly (L-lactide)-caprolactone solution or a polyurethane solution; S5: using a poly (L-lactide-caprolactone) solution or a polyurethane solution as a spinning solution, performing electrospinning on the surface of the mold with the artificial blood vessel inner layer, and drying to obtain a semi-finished mold; S6: removing the inner lining layer in the semi-finished mold, taking out the cylindrical mold, and obtaining the convex double-layer composite small-caliber artificial blood vessel.

2. The artificial blood vessel according to claim 1, wherein In the steps S1 and S3, the speed of withdrawing the demoulding liquid is 500-2000 μm / s.

3. The artificial blood vessel according to claim 1, wherein: The stripping liquid is a polyvinyl alcohol solution and / or a polyethylene oxide solution.

4. The artificial blood vessel according to claim 1, wherein In step S2, both ends of the mold with the dip coating are immersed in water respectively to remove the dip coating.

5. The artificial blood vessel according to claim 1, wherein: In step S4, the speed of withdrawing the dipping liquid is 800-1200 μm / s.

6. The artificial blood vessel according to claim 1, wherein: The concentration of the dipping solution is 5.5-6.5 wt%.

7. The artificial blood vessel according to claim 1 or 6, characterized in that: The dipping solution also includes a pore-forming agent.

8. The artificial blood vessel according to claim 1, wherein: The concentration of the spinning solution is 7.5-8.5 wt%.

9. The artificial blood vessel according to claim 1, wherein: In step S5, the electrospinning parameters are: the injection pump propulsion speed is controlled at 0.5-1.5 mL / h, the high-voltage DC power supply voltage is controlled at 10-12 kV; the distance between the spinneret and the receiving device is 15-20 cm, the collection device speed is 300-500 rpm, the spinning temperature is 28-32°C, and the spinning relative humidity is less than 65%.

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